Low numerical aperture profilometry via photometric stereo using multimedia projector as light source

Abstract

This paper probes the feasibility of employing photometric stereo technique in obtaining surface depth information of microscopic objects. The said technique is based on the changes in the reflectivity map of an object with the direction of illumination. It is carried out using an inverted microscope wherein a commercial media projector provides the lighting. Illumination is controlled by switching from one projected slide to another. With the system, it is facile to extend from a 4-light source to an 8-light source setup. The technique is employed to visualize the surface profiles of a semiconductor device and of beetle carapace.